This invention relates to medico-surgical instruments. The invention is, more particularly, concerned with instruments for use in detecting the epidural, or other body, space.
In epidural anaesthesia an anaesthetic drug is administered through a small-bore cannular or needle, one end of which is located within the patient's epidural space. The cannula is correctly positioned by means of a hollow-bore Tuohy needle that is pushed through the spinal ligaments into the epidural space, the cannula then being fed through the bore of the needle which is subsequently withdrawn to leave the cannula in place. In the past, difficulties have been experienced in correctly positioning the Tuohy needle. If the Tuohy needle is pushed too far it penetrates the matter underlying the epidural space and discomfort can be caused to the patient.